The present invention is in the field of printers and copiers. Specifically this invention relates to paper supply platforms.
Paper often has what is called curl, which is the edges of the paper not being level with the center of the paper. Moderate curl is adequately handled with present sheet feeders. However, many factors can cause a curl which exceeds that which can be fed reliably. Sensitivity to curl is greatest with very light paper, and very heavy paper.
Further, certain environmental conditions can cause excess curl. When a stack of paper is exposed to a dry environment, the stack dries from the exposed surfaces inward toward the center of the stack. For sheets in the middle of the stack, this results in the edges of the sheets drying first. Since most papers shrink when they dry out, this results in the edges of the sheet being ‘smaller’ than the center of the sheets which haven't dried out as much. This results in a “dish” curl, or “oilcanning” whereby the sheet deflects out of plane, with edges either rising or falling. When such paper is stacked in a paper supply this generally results in the edges of the paper being higher than the center of the paper due to the weight of the stack in the center. For the most reliable feeding of paper, the center of the paper should be higher than the edges of the paper (in a top feeding vacuum device).
A paper supply tray is desired which would allow for reliable feeding of paper with a wide range of curl, and which preferably would orient all paper with curl such that the center of the paper stack is higher than the edges of the paper stack for the most reliable feeding.